The present invention relates to a variable vane arm/unison ring/vane attachment system for use in a variable incidence vane system in a gas turbine engine.
A variable vane arm 11 is used to control the incidence angle of vanes 8 in the compressor section of gas turbine engines. The vanes 8 are arranged as a stage set around the circumference of the compressor. The vane arm 11 attaches to each vane spindle 26 which rotates in a bearing mounted in the compressor case. The set of vanes 8 in a stage are actuated by a circumferential synchronizing or unison ring 15 that rotates about the engine axis. The vane arm 11 imparts motion from the synchronizing ring 15 to the vane spindle 26 and has to accommodate all the relative motion between the ring 15 and the vane 8.
A current vane arm/unison ring attachment system 10 is illustrated in FIG. 1. The vane arm 11 used therein incorporates a brazed bushing 12 which has chamfered reliefs 14 to allow for differences in kinematic motion of the vane arm 11, which travels in a planar arc relative to the engine circumference, and the unison ring 15 which rotates about the engine center line and translates axially. The bushing 12 interfaces with a pin 16 attached to the unison ring 15 by means of a single swage and a tack weld.
Referring now to FIG. 2, the vane arm 11 has a non-tapered claw feature 20 which has two curved members 22 and 23 for engaging slots 24 and 25 in a vane spindle 26.
The current vane arm/unison ring attachment system suffers from a number of deficiencies including wear between the pin and vane arm bushing, a potential for relative vibration at the joint interface between the pin 16 and the unison ring 15, and slop at the inner diameter of the unison ring 15 which causes wear at the mating surface.